1. Field of the Invention
The present invention relates to a temperature controlled electrical power supply apparatus and in particular to an electrical current supply apparatus for use in heating the conducting foil of carpet joining tape. In the particular type of carpet joining tape considered here the conducting foil is heated by passage of electrical current to melt adhesive on the foil for adhesion to the back of the carpet. It should be evident that the apparatus of the invention, while described below in relation to a carpet joining tape, is suitable for use in any other application where it is desired to maintain a substantially constant temperature over a period of time.
2. Prior Art
The existing electrical apparatus for heating the conducting foil of carpet tape comprises an adjustable high current supply. The user connects supply leads to the foil and sets the current to the desired level by a control knob on the apparatus. The major problem occurring with the existing apparatus stems from the fact that, as the foil heats up, its resistance varies considerably causing the current to fluctuate to the extent that the user is continually having to re-adjust the control knob in order to maintain the current at a level whereby the temperature of the foil is suitable. Invariably the user is unable to maintain the temperature at a suitable level while performing the task of joining the carpet edges. Hence the adhesive either does not melt properly or it becomes too hot making it difficult to work with and delaying the curing process. Needless to say it is most inconvenient for the user to be continually re-adjusting the control knob since this usually involves moving a substantial distance to the apparatus particularly when working with long carpet joints.